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Anatomy 2 - Digestive
Digestive system for exam 3
Undergraduate 1

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What are the main functions of the digestive system?

ingestion - the taking of the food via the mouth.

digestion- the mechanical and chemical break down of food by chewing and enzymes.

absorption- food passes through the intestinal wall into the blood system and

elimination- the removal of indigested waste


What are the six digestive processes?



ingestion (taking food into the mouth)

 secretion (the act of expelling a liquid. The cells lining the GI tract secrete about 9 liters (9.5 quarts) of water, acid, buffers, and enzymes each day to lubricate the canal and aid in the process of digestion)

 propulsion (consists of alternating contraction and relaxation of smooth muscle in the walls of the GI tract to squeeze food downwards)


digestion ( has two parts, mechanical and chemical. Mechanical

digestion is chewing up the food and your stomach and smooth intestine churning the food, while chemical digestion is the work the enzymes do when breaking large carbohydrate, lipid, protein and nucleic acid molecules down into their subcomponents -these and others are the nutrients),

absorption (ccurs in the digestive system when the nutrients move from the gastrointestinal tract to the blood or lymph)

defecation ( process of expelling what the body couldn't use.)

What are the main functions of the digestive system?


ingestion - the taking of the food via the mouth.

digestion- the mechanical and chemical break down of food by chewing and enzymes.

absorption- food passes through the intestinal wall into the blood system and

elimination- the removal of indigested waste




·         Know the layers (tunics) of the GI tract. Be able to put them in order & know the functions of each tunic.


1. Mucosa (a mucous membrane that lines the inside of the digestive tract from

mouth to anus. Depending upon the section of the digestive tract, it protects the GI tract wall, secretes substances, and absorbs the end products of digestion)

2. Submucosa (lies outside the mucosa. It consists of areolar connective tissue

containing blood vessels, lymphatic vessels, and nerve fibers.)

3. Muscularis externa (a layer of muscle. In the mouth and pharynx, it

consists of skeletal muscle that aids in swallowing. In the rest of the GI tract, it consists

of smooth muscle (three layers in the stomach, two layers in the small and large

intestines) and associated nerve fibers. The smooth muscle is responsible for

movement of food by peristalsis and mechanical digestion by segmentation. In some

regions, the circular layer of smooth muscle enlarges to form sphincters, circular

muscles that control the opening and closing of the lumen (such as between the

stomach and small intestine).

4. Serosa (a serous membrane that lines the outside of an organ. The following

serosae are associated with the digestive tract:

The adventitia is the serous membrane that lines the esophagus.

The visceral peritoneum is the serous membrane that lines the stomach, large

intestine, and small intestine.

The mesentery is an extension of the visceral peritoneum that attaches the small

intestine to the rear abdominal wall.

The mesocolon is an extension of the visceral peritoneum that attaches the large

intestine to the rear of the abdominal wall.

The parietal peritoneum lines the abdominopelvic cavity (abdominal and pelvic

cavities). The abdominal cavity contains the stomach, small intestine, large

intestine, liver, spleen, and pancreas. The pelvic cavity contains the urinary bladder,

rectum, and internal reproductive organs.)


Compare & contrast the muscle movements of peristalsis & segmentation

They are both a type of mechanical digestion that is involved in the gastrointestinal tract.


Peristalsis is the slow and gradual movement of food through the digestive system. The food is crushed and propelled in one direction as smooth muscle contracts and forces the food along the gastrointestinal tract.


Peristalsis is not to churn, but to slowly move food along towards the large intestine, however, segmentation is the local mixing of food with enzymes and intestinal juices (from pancreas etc). Therefore the food is mixed and and exposed to absorptive cells as it moves along

How is the digestive system controlled?

By hormone and nerve regulators.



 gastrin, secretin, and cholecystokinin (CCK):

  • Gastrin causes the stomach to produce an acid for dissolving and digesting some foods. It is also necessary for the normal growth of the lining of the stomach, small intestine, and colon.
  • Secretin causes the pancreas to send out a digestive juice that is rich in bicarbonate. It stimulates the stomach to produce pepsin, an enzyme that digests protein, and it also stimulates the liver to produce bile.
  • CCK causes the pancreas to grow and to produce the enzymes of pancreatic juice, and it causes the gallbladder to empty.
Extrinsic (outside) nerves come to the digestive organs from the unconscious part of the brain or from the spinal cord. They release a chemical called acetylcholine and another called adrenaline. Acetylcholine causes the muscle of the digestive organs to squeeze with more force and increase the "push" of food and juice through the digestive tract. Acetylcholine also causes the stomach and pancreas to produce more digestive juice. Adrenaline relaxes the muscle of the stomach and intestine and decreases the flow of blood to these organs.

Even more important, though, are the intrinsic (inside) nerves, which make up a very dense network embedded in the walls of the esophagus, stomach, small intestine, and colon. The intrinsic nerves are triggered to act when the walls of the hollow organs are stretched by food. They release many different substances that speed up or delay the movement of food and the production of juices by the digestive organs.
What is the importance of the mesenteries in the digestive system?


double layer of peritoneum that suspends the jejunum and ileum from the posterior wall of the abdomen.
Routes for blood vessels, lymphatics, & nerves
Holds organs in place & stores fat


What are the four classes of teeth?


You have eight incisors. They are in the front and the teeth you see the most. They are made for tearing food.


These are the pointy teeth right beside your incisors. You have four of these. They are for grasping and tearing food . When you bite into a piece of pizza, the incisors and canines work together to cut the cheese away! They are called canines because you often see them among dog's teeth.


These are the next teeth you find as you go back along your teeth. They are the flat, stubby teeth that grind food down for swallowing.


Molars are behind premolars. They are wide and flat, perfect for grinding up food.

What are three salivary glands called and what are the functions of salivary glands?

the parotid

the submandibular

the sublingual glands

Also, Intrinsic (buccal) salivary glands scattered in oral mucosa

The salivary glands make saliva. Saliva keeps the mouth and other parts of the digestive system wet. It also helps break down carbohydrates (with salivary amylase, formerly known as ptyalin) and keeps food wet and slippery so it can go down from the oro-pharynx to the esophagus to thestomach. It also cleanses the mouth.

What is the dental formula?

Dental formulas record the number of each type of tooth in one half of the upper and lower jaw using shorthand. Since the left side of the jaw has the same number as the right, only one side is counted. Mammals are heterodont, meaning there are different shapes or types of teeth, denoted as I, C, P, and M (incisors, canines, premolars, and molars).

The permanent or adult dental formula of humans is I 2/2, C 1/1, P 2/2, M 3/3 (x2= 32). This is the notation format for dental formulas in mammalogy.

The dental formula for humans following the format for anthropology/primatology would be 2:1:2:3/2:1:2:3, where the numbers correspond to I:C:P:M (upper)/I:C:P:M (lower).


·         What could a person use the teeth class & dental formula to determine?

They could determine the age and lifestyle of a person.
Where do carbohydrates begin to digest and also end?

carbohydrates begin digesting in the mouth with the saliva


The end product of carbohydrate digestion is mainly glucose together with some fructose, glucose, and galactose. 

Where do lipids digestion begin and end?
The stomach contains Gastric Lipase to break down lipids

the liver secretion( bile) contains Hepatic lipase to digest lipids....

all the lipases act the same way on lipids and break them down. The lipids are broken down into cholesterols and fatty acids,,,,,,lipids are long chains of fatty acids(saturated and unsaturated)
where does protein digestion begin and end?

The protein is first digested in the stomach, where it is broken down by the acid and enzymes. 

Then it goes into the small intestine, where enzymes from the pancreas help to break it down further into individual amino acids. 

The organs that assist with protein digestion are bold.

Where do nucleic acids digestion begin and end?
Both DNA and RNA, present in the nuclei of cells forming the ingested foods, are hydrolyzed to their nucleotide monomers by pancreatic nucleases present in pancreatic juice. The nucleotides are then broken apart by intestinal brush border enzymes, which release their free bases, pentose sugars, and phosphate ions.


    What is the function of the esophagus? What gets digested here?


Food is passed through the esophagus by using the process of peristalsis. Specifically, it connects the pharynx, which is the body cavity that is common to the digestive factory and respiratory system with the stomach, where the second stage of digestion is initiated. 
The passage food takes from mechanical digestion in the mouth to digestion in the stomach. 

It's function though is to help and provide a place for the food to travel down to your stomach.


Food does not digest in the esophagus.

What type of digestion occurs in the mouth?

Both mechanical and chemical. Chewing, also called mastication, is using your teeth with the help of your tongue to break down food into smaller particles, and the other a chemical process where salivary amylase which is a digestive enzyme that helps break down carbohydrates.


·      What is the function of the stomach? What type(s) of digestion occur(s) here? What chemicals are secreted here? 


The stomach's main function is digestion. It does this by:

  • Storing the food we eat.
  • Breaking down the food into a liquidly mixture called chyme.
  • Mixing enzymes which is are chemicals that break down food.
  • Slowly empties that liquidly mixture into the small intestine.


The stomach uses pepsin (enzyme) and peptidase (another enzyme) to break down proteins in your food. The acid released by the stomach doesn't break down food it only provides a good environment for the enzymes to work in. By this point the food is mushy and the stomach then passes this mixture on to the small intestine which will further break down the food.


Both chemical and Mechanical digestion occur. Mechanical (churrning of the stomach) and Chemical (Acid to digest proteins)

Hydrochloric acid produced by the stomach aids the enzymes to digest the protien

What is the value of an acidic stomach?

The normal stomach pH is around 1.5-2.


It breaks down food we eat.

What is the cause of an ulcer?

Most are caused by Helicobacter pylori bacteria
bacterial infection.
excessive gastric acid secretion. 
use of certain anti-inflammatory medicines.

What is the function of the small intestine?
The small intestines are responsible for absorbing most of the nutrients found within your food. By the time ingested food reaches the small intestine, it has been mechanically broken down into a liquid. As this liquid flows across the inner surface of the small intestine (which has many small folds to increase the surface area), nutrients within the food come into contact with the many small blood vessels which surround the small intestine. This blood then leaves the small intestine, carrying away nutrients, water electrolytes, vitamins, minerals, fats and medications to the entire body. It can take three to six hours for a meal to pass from one end of the small intestine to the other, and that is dependent on the makeup of the food passing through; meals containing a lot of fiber move more quickly. 

The primary function is absorption of nutrients from food.

What is the function of the liver?

produces bile for the break down of fats

  • converts glucose (sugars) to glycogen (stored sugar)
  • filters harmful substances from the blood such as alcohol
  • storage of vitamins and minerals (Vitamin A, D, E, & K)
  • responsible for producing cholesterol. produces about 80% within the body.
  • matures red blood cells 

Functions of liver: 
1. Converts toxic product into nontoxic ones. 
2. Liver actively participates in metabolism of Carbohydrates, Fats, Proteins, Vitamins and Minerals. 
3. It excretes bile pigments, bile salts, cholesterol through bile. 
4. It synthesizes plasma proteins. 
5. It stores glycogen, vitamin A, D and B12 and trace elements

What is a liver lobule?
A hepatic lobule is a small division of the liver defined at the histological scale. It should not be confused with the anatomic lobes of the liver (caudate lobe, quadrate lobe, left lobe, and right lobe), or any of the functional lobe classification systems.

·         What are hepatocytes & what do they do?


They are liver cells.


Protein synthesis

  • Protein storage
  • Transformation of carbohydrates
  • Synthesis of cholesterol, bile salts and phospholipids
  • Detoxification, modification, and excretion of exogenous and endogenous substances

The hepatocyte also initiates formation and secretion of bile.

What is bile? What does it do? Where is it stored?

a digestive juice secreted by the liver and stored in the gallbladder;

aids in the digestion of fats

It is stored in the gallbladder

What are the functions of the pancreas?
It manufactures and secretes digestive enzymes such as amylase, which digests starch. It also produces lipase, which breaks down fats, and trypsin, a protein processor. The pancreas creates and secretes insulin, glucagon and other hormones. Insulin and glucagon are especially important for the maintenance of blood sugar, as insulin lowers the blood sugar and glucagon increases the blood sugar according to the body's needs
What chemicals do the Pancreas secrete? What do they do?


  1. Insulin (elps turn sugar in your body into energy )
  2. Glucagon (to react to a situation where there is a low level of blood sugar present. The release of glucagon into the bloodstream helps to restore blood glucose levels back to a point that is considered acceptable for the general function of the body.)
  3. Somatostatin (inhibits hormones secretion)


What is the importance of the sphincter?
Sphincters prevent materials from moving backward or allow materials to move from one segment of the digestive system into the next a little at a time.
What is the pathway of food?
Mouth > Pharynx > Esophagus > stomach > duodenum (liver/gall bladder/ pancreas) > jejunum > ileum > large intestine > rectum > anus
What is the function of the large intestine?
the large intestine is the thick, lower end of the digestive system, containing the appendix, colon and rectum. Its principle function is to reabsorb water and maintains the fluid balance of the body. Certain vitamins are also taken in through the large intestinal wall. 

Further down the intestine, in the rectum, faeces are stored waste before it is eliminated. Another function is to process undigestible material (fibre), which makes up the bulk of the waste products.
What features does the large intestine have to allow it to perform its functions?

1.Teniae coli – 3 bands of longitudinal smooth muscle in muscularis
2.Haustra -pocketlike sacs
3.Epiploic appendages - fat-filled pouches of visceral peritoneum

What do the following chemicals do? amylase, pepsin, protease, lipase, bile, nuclease?

amylase: breaks down starches.

pepsin: breaks proteins down so we can digest them.

lipase: a dietary enzyme that acts in the intestine to break down fats and oils into forms that the body can metabolize. 

bile: aids in the digestion of fats 

nuclease: enzymes that break down nucleic acids into strands of DNA

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